Memory controller system with non-volatile backup storage

ABSTRACT

The present invention is directed to computer storage systems and methods thereof. More specifically, embodiments of the present invention provide an isolated storage control system that includes both a non-volatile memory and a volatile memory. The non-volatile memory comprises a data area and a metadata area. In power failure or similar situations, content of the volatile memory is copied to the data area of the non-volatile memory, and various system parameters are stored at the metadata area. When the system restores its operation, the information at the metadata area is processed, and the content stored at the data area of the non-volatile memory is copied to the volatile memory. There are other embodiments as well.

CROSS-REFERENCES TO RELATED APPLICATIONS

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STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

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REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK

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BACKGROUND OF THE INVENTION

The present invention is directed to computer storage systems andmethods thereof.

Over the last few decades, the use of communication networks exploded.In the early days Internet, popular applications were limited to emails,bulletin board, and mostly informational and text-based web pagesurfing, and the amount of data transferred was usually relativelysmall. Today, Internet and mobile applications demand a huge amount ofbandwidth for transferring photo, video, music, and other multimediafiles. For example, a social network like Facebook processes more than500 TB of data daily, and that number is growing. With such high demandson data and data transfer, existing data communication systems need tobe improved to address these needs. Companies built large server farms,where large numbers of computers together provide computational power toremote clients. Speed and reliability are two important aspects ofserver computers. For example, servers often has mechanism for databackup in situations such as power failure.

Over the past, conventional techniques have been proposed to improvecomputer reliability. Unfortunately, these conventional techniquesinadequate, as explained below. Therefore, improved system and methodsfor data reliability are desired.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to computer storage systems andmethods thereof. More specifically, embodiments of the present inventionprovide an isolated storage control system that includes both anon-volatile memory and a volatile memory. The non-volatile memorycomprises a data area and a metadata area. In power failure or similarsituations, content of the volatile memory is copied to the data area ofthe non-volatile memory, and various system parameters are stored at themetadata area. When the system restores its operation, the informationat the metadata area is processed, and the content stored at the dataarea of the non-volatile memory is copied to the volatile memory. Thereare other embodiments as well.

According to an embodiment, the present invention provides a memorysystem that includes a non-volatile memory, which includes a data areaand a metadata area. The metadata area is predefined to store systemparameters. The system also includes a volatile memory. The systemincludes a backup power module. The system additionally includes acontroller module, which has a host interface and a plurality ofregisters. The controller module is configured to transferring datareceived from the host interface to the volatile memory. In a SAVEevent, the controller module is configured to cause the non-volatilememory to store at least content of the plurality of registers andsignature data at the metadata area and store content of the volatilememory at the data area. In a RESTORE event, the controller module isconfigured to determine a validity of the content stored at the dataarea using at least the signature data, and the controller module causesthe content stored at the data area to be copied to the volatile memoryif the content at the data area is determined to be valid.

a method for preserving volatile memory data for a memory system. Themethod includes defining a data area and a metadata area on anon-volatile memory. The method also includes detecting a failure event.The method includes allocating at least a portion of the data area forstoring a content of a volatile memory. The method includes storing alocation of the portion of the data area at the metadata area. Themethod further includes storing operating parameters of the memorysystem at the metadata area. The operating parameters includeinformation related to characteristics of the volatile memory. Themethod further includes storing the content of the volatile memory atthe portion of the data area. The method additionally includes updatingone or more signature data stored at the metadata area.

According to another embodiment, the present invention provides a methodfor restoring operation and data for a memory system. The methodincludes obtaining a signature data stored at a metadata area of anon-volatile memory, which includes a metadata area and a data area. Themethod further includes comparing the signature data to a reference datato determine whether a previous backup event is valid. If the backupevent is valid, the following steps are performed:

-   -   obtaining operating parameters from the metadata area;    -   operating a controller module in accordance with the operating        parameters;    -   copying a first content stored at the data area to a volatile        memory. On the other hand, if the backup event is invalid, the        following steps are performed:    -   initializing the metadata area using at least a predetermine set        of parameters;    -   initializing the memory system.

It is to be appreciated that embodiments of the present inventionprovides numerous advantages over existing technologies. Among otherthings, by storing both operating parameters of the memory systemcontrollers and content of the volatile memory, back and restoreoperations can be performed reliability and efficiently. In addition,the memory systems according to embodiments of the present invention canbe implemented and readily utilized by existing systems. For example,from host system perspective, a memory system according to embodimentsof the present invention operates much like an existing volatile memory,with the added benefit of providing backup functionality withoutadditional inputs from the memory host system. There are otherembodiments as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating an iSC controller systemaccording to an embodiment of the present invention.

FIG. 2 is a simplified diagram illustrating operation of a controllermodule data path according to an embodiment of the present invention.

FIG. 3 is a simplified flow diagram illustrating a processing for savingvolatile memory content according to an embodiment of the presentinvention.

FIG. 4 is a simplified flow diagram illustrating a processing forrestoring volatile memory content according to an embodiment of thepresent invention.

FIG. 5 is a simplified diagram illustrating a controller module 500according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to computer storage systems andmethods thereof. More specifically, embodiments of the present inventionprovide an isolated storage control system that includes both anon-volatile memory and a volatile memory. The non-volatile memorycomprises a data area and a metadata area. In power failure or similarsituations, content of the volatile memory is copied to the data area ofthe non-volatile memory, and various system parameters are stored at themetadata area. When the system restores its operation, the informationat the metadata area is processed, and the content stored at the dataarea of the non-volatile memory is copied to the volatile memory. Thereare other embodiments as well.

As explained above, providing reliability is an important aspect of dataservers and other applications. For example, power failure is a commonscenario where unsaved information is lost. When information is storedin non-volatile memory, the amount of data loss is often small, andsometimes negligible. With server applications, where large amount ofdata, if not all the data, is stored in volatile memory (e.g., RAM) forspeed, data loss can be catastrophic in the event of power or systemfailure.

The following description is presented to enable one of ordinary skillin the art to make and use the invention and to incorporate it in thecontext of particular applications. Various modifications, as well as avariety of uses in different applications will be readily apparent tothose skilled in the art, and the general principles defined herein maybe applied to a wide range of embodiments. Thus, the present inventionis not intended to be limited to the embodiments presented, but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

In the following detailed description, numerous specific details are setforth in order to provide a more thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatthe present invention may be practiced without necessarily being limitedto these specific details. In other instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which arefiled concurrently with this specification and which are open to publicinspection with this specification, and the contents of all such papersand documents are incorporated herein by reference. All the featuresdisclosed in this specification, (including any accompanying claims,abstract, and drawings) may be replaced by alternative features servingthe same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Furthermore, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of” or “act of” in the Claims herein is notintended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

Please note, if used, the labels left, right, front, back, top, bottom,forward, reverse, clockwise and counter clockwise have been used forconvenience purposes only and are not intended to imply any particularfixed direction. Instead, they are used to reflect relative locationsand/or directions between various portions of an object.

Embodiments of the present invention provides an isolation storagecontroller (iSC) system that includes a non-volatile DIMM memory(NVDIMM) that includes both volatile memory and non-volatile memory,where the non-volatile memory is specifically configured to preserveinformation stored at the volatile memory in the event of power or othertypes of failures. The iSC system is capable of selectively backup andrestore the content of the volatile memory, and to determine theintegrity of the information stored at the non-volatile memory. Forexample, non-volatile memory is implemented using flash memory andvolatile memory is implemented using SDRAM, but it is to be understoodthat other types of components may be used as well.

FIG. 1 is a simplified diagram illustrating an iSC controller systemaccording to an embodiments of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown in FIG. 1, an iSCsystem 100 is connected to the host memory controller 101. For example,the host memory controller 101 uses the iSC system 100 as a non-volatileDIMM (NVDIMM) module that is capable of preserving data in failurescenarios. The iSC system 100 includes a controller module iSC01 102, avolatile memory 103 (e.g., SDRAM), a non-volatile memory 104 (e.g.,flash memory, SSD, etc.), and a backup power 105.

The controller module 102 is connected to other modules of the iSCsystem 100 via its interfaces. The controller module iSC01 102 comprisesa host Interface, an SDRAM interface, and a non-volatile memoryinterface. In various implementations, the host interface of thecontroller module 102 connects to system memory host controller 101through a DIMM edge connector. Depending on the application, otherconnections between the host interface and the host memory controller101 can be used as well. The SDRAM interface of the controller module102 connects to SDRAM 103. For example, the SDRAM 103 may include anumber of memory modules, and the controller module 102 can be connectedto the SDRAM 103 via various types of bus lines. For example, the hostinterface and SDRAM interface of the controller module performload-reduction memory buffer (MB) operation. Also, other types ofvolatile memory device can be used as well.

The non-volatile memory interface connects the controller module 102 toa non-volatile memory 104. Non-volatile memory 104 can be implementedusing various types of devices, such as flash memory, solid state disk,and/or others. The non-volatile memory 104 is shown as a part of the iSCsystem 100, but it can be implemented using external storage devices.For example, the non-volatile memory 104 can be a part of the serverstorage and external to the iSC system 100.

In a specific embodiment, the non-volatile memory 104 has a capacitygreater than the volatile memory module 103 and is thus able to preservethe entirety of information stored at the volatile memory module 103.The interface between the controller module 102 and the non-volatilememory 104 is high-speed and low-latency. In a specific embodiment, aSATA interface, which can provide a bandwidth of 6 Gbps, is used toimplement the non-volatile memory interface of the controller module102. For example, the SATA interface is used to preserve SDRAM content(e.g., backup image) during a system power failure situation. Thenon-volatile memory interface of the controller module 102 can beimplemented using other types of bus interfaces as well, such as PCIExpress, and others.

As shown in FIG. 1, the controller module 102 is electrically coupled toa power backup 105. Depending on the application, the backup power 105may store enough power for sustaining the iSC system 100 through shortpower failure. In certain embodiments, the backup power 105 has enoughpower to allow data stored at the volatile memory 103 to be saved to thenon-volatile memory 104. In various embodiments, the backup power 105 isconstantly recharged.

In addition to power failures, there can be different types ofsituations or events that trigger backing up the content stored at thevolatile memory to the non-volatile memory. For example, the backing upprocess is triggered by a predetermined “SAVE” event. When a SAVE eventtrigger (e.g., due to system power failure or software initiated) isreceived, the controller module 102 performs SDRAM reads and saves SDRAMcontent to the non-volatile memory 104 through its non-volatile memoryinterface. Since the non-volatile memory 104 retains data without power,the volatile memory content is preserved even when the system completelyloses power. For example, the backup power 105 of the iSC system 100 canbe implemented as a temporary power source, such as a super capacitor.The backup power 105 supplies the power needed for the SAVE operation.Once the SAVE operation is complete the backup power is no longerneeded.

It is to be appreciated that the non-volatile memory 104, operating inconjunction with the controller module 102, is configured to storecontents of the volatile memory 103 and system settings and parameters.In a specific embodiment, the non-volatile memory 104 has a storagecapacity that is multiple size of the volatile memory 103, and thus iscapable of storing more than one instance of the volatile memorycontent.

The content stored at the non-volatile memory can be restored back tothe volatile memory. In various embodiments, after system power isrestored, a “RESTORE” event trigger is sent to the controller module102. The RESTORE operation restores volatile memory content using thesaved image stored at the non-volatile memory through the volatile andnon-volatile interfaces of the controller module 102. For example, theSAVE and RESTORE operation performed by the iSC system 100 does not needparticipation from the host system (e.g., host memory controller 101).From system perspective, the content of the volatile memory is intactand the non-volatile memory appears to be non-volatile. In addition,system parameters and/or settings may be loaded from the non-volatilememory during the RESTORE operation.

It is desirable and sometimes necessary to have system or chipconfiguration parameters preserved over a loss of power to the system orchip. One such example is the CMOS RAM in a traditional PC design. Itcontains critical configuration parameters for system boot. Its contentis preserved by a small button or rechargeable battery so it remainspersistent over a power loss event.

The SAVE and RESTORE operations described above are a simplification.For reliability purposes, many things happen when data are transferredbetween the non-volatile memory 104 and the volatile memory 104. Whenthe non-volatile memory 104 saves the content of volatile memory 103,the controller module 102 also saves relevant system information andconfiguration parameters to the metadata field of the non-volatilememory 104. When the controller module 102 retrieves information fromthe non-volatile memory 104 to restore the volatile memory, thecontroller module 102 first processes the information stored at themetadata field of the non-volatile memory 104.

It is to be appreciated that the preservation of configurationparameters and system information over a power loss event is importantto the operation of the controller module 102 and the iSC system 100 asa whole. The SAVE and RESTORE operations are to be performedautonomously while the system host controller (e.g., host memorycontroller 101) may have lost its power and/or is not yet operational.To accomplish this, the iSC system 100 uses a metadata scheme that doesnot require battery backup.

The controller module 102 manages the non-volatile memory 104 andreserves a predetermined number of data blocks (e.g., 512-byte sectors)in the metadata area of the non-volatile memory 104. According tovarious implementations, the metadata area is hidden and not accessiblefor user data (e.g., content of volatile memory 103, or SDRAM images)storage. Typically, critical volatile memory parameters (e.g.,latencies, frequencies, organization, etc.) and important control andstatus data are saved to the metadata area of the non-volatile memory104. In contrast, these parameters are typically stored in the chipregisters of conventional systems. For example, the metadata area isupdated with various system and volatile memory parameters during systeminitialization, at the beginning and the end of a SAVE or RESTOREoperation, or when power loss is detected.

To provide an example, after a power-on reset, the controller module 102establishes communication with the non-volatile memory 104 and searchesfor valid metadata. If valid metadata is found, the controller module102 restores its corresponding internal registers with the metadatacontent. It is to be appreciated that these registers of the controllermodule 102 are effectively persistent, as their content survives powerloss events.

As explained above, the system 1 operates as an NVDIMM. Instead of theisolated controller implementation illustrated in FIG. 1, otherimplementations as possible as well, according to existing techniques.For example, field-programmable gate array (FPGA) can be used inimplementing NVDIMM systems. It is to be appreciated that embodiments ofthe present invention offer numerous advantages over existing FPGA basedimplementations. For example, since an FPGA does not have an integratedmemory buffer of isolated controller, FPGA based implementations rely onswitches to share the command/address and data buses with the hostcontroller and C/A (command/address) buffer. Existing FPGAimplementations also require additional program flash for the FPGAitself. As a result, FPGA based implementations, in comparison toisolated controllers according to embodiments of the present invention,have higher number of components, consume more power, and take up morereal estate on a space limited NVDIMM.

Additionally, NVDIMM systems implemented according to embodiments of thepresent invention provides performance advantages over FPGA based NVDIMMsystems. In FPGA implementations, insertion of switches in the highspeed command/address and data paths causes degradation of signalintegratity, which consequently limits the maximum memory speeds (orfrequency) that they can operate. As an example, for DDR3 NVDIMM theFPGA-based NVDIMM speeds is limited to DDR3-1333 or lower. In contrast,isolated controller based NVDIMM systems according embodiments of thepresent invention can run at maximum speed of DDR3-1866, represents a40% performance advantage over the FPGA-based implementation in systemmemory access. There are other benefits as well.

FIG. 2 is a simplified diagram illustrating operation of a controllermodule data path according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims. One of ordinary skill in the art would recognizemany variations, alternatives, and modifications. As shown in FIG. 2,the controller module 202 interfaces with the non-volatile memory 204.For example, the controller module 202 may be implemented using thecontroller module 102 in FIG. 1; the non-volatile module 204 may beimplemented using the non-volatile memory 104 in FIG. 1.

As shown in FIG. 2, the non-volatile memory 204 comprises a user dataarea 211 and a metadata area 212. The metadata area 212 is predefinedwith data fields for storing various parameters related to components(e.g., controller module, volatile memory, etc.) of the iSC system. Theuser data 211 is configured to store one or more instances of volatilememory content. As explained above, the non-volatile memory 204 may beimplemented using an external storage, and may thus store otherinformation.

The controller module 202, as shown in FIG. 2, includes a table RAM 221,sequence execution finite state machine (FSM) 222, command execution FSM223, and a registers 224. The operation of the controller module 202 isexecuted by the command execution FSM 223. Operation parameters andstates of the FSMs of the controller module 202 are stored at theregisters 224 and continuously updated as the controller module 202operates. In power failure or similar situations, the controller module202 sends the content of the registers 224 and other relevantinformation to the non-volatile memory 204, and non-volatile memory 204stores them in the metadata area 212.

It is to be appreciated that the content of the metadata area 212 helpsrestore functionalities of the iSC system. For example, the controllermodule 202 uses the metadata area 212 to backup register values andvarious parameters needed to resume operation. In addition, as explainedbelow, the metadata area has data blocks for checking validity of thecontent stored at the data area 211 and the metadata area 212. Accordingto various implementations, the metadata area 212 includes informationfrom both the table ram 221 and the registers 214.

Table 1 below shows the content stored at the metadata area according toan implementation. It is to be appreciated the metadata content may beimplemented in other ways as well.

TABLE 1 Name Offset Description Signature Low ‘h0000 Lower 16 bits ofthe NV Signature register Signature High ‘h0002 Upper 16 bits of the NVSignature register NV Status 0 ‘h0004 16-bit NV Status 0 register valueBrownout Count ‘h0006 16-bit Brownout Count register value Start Address‘h0008 16-bit Start Address register value End Address ‘h000A 16-bit EndAddress register value LBA0 Low ‘h000C 16-bit LBA0 Low register valueLBA0 Mid ‘h000E 16-bit LBA0 Mid register value LBA0 High ‘h0010 16-bitLBA0 High register value LBA1 Low ‘h0012 16-bit LBA1 Low register valueLBA1 Mid ‘h0014 16-bit LBA1 Mid register value LBA1 High ‘h0016 16-bitLBA1 High register value Scratchpad0 ‘h0018 16-bit Scratchpad0 registervalue Scratchpad1 ‘h001A 16-bit Scratchpad1 register value NV Debug 0‘h001C 16-bit NV Debug 0 register value NV Debug 1 ‘h001E 16-bit NVDebug 1 register value NV Debug 2 ‘h0020 16-bit NV Debug 2 registervalue SDRAM ‘h0022 - 003F SDRAM parameters such as latencies, controlfrequencies, and organization Context 1 ‘h0040 - 006F SDRAM trainingparameters for Training context 1 Context 2 ‘h0070 - 009F SDRAM trainingparameters for Training context 2 Context 3 ‘h00A0 - 00CF SDRAM trainingparameters for Training context 3 Context 4 ‘h00D0 - 00FF SDRAM trainingparameters for Training context 4 Table RAM ‘h0100 - 02FF Operation andcommand table data.

As shown in Table 1, the content includes status, count, address, andmanagement data. The “Signature Low” and “Signature High” data are usedto validate metadata. For example, the metadata area and the use thereofprovide a fail-safe mechanism for status register. Additionally, themetadata area, as defined in Table 1, can store debugging information.Among other things, saving the content of debug registers in themetadata provides a benefit of making debug and workaround settingssticky, and therefore the settings do not need to be re-applied afterpower cycle or chip reset. Similar benefits apply to the control andaddress registers.

In an implementation, two 16-bit registers are used to form a 32-bit NVSignature register. The Signature value in this register is stored as apart of the metadata saved after a successful SAVE or RESTORE operation.In a power-on reset operation, the Signature value is retrieved frommetadata area of the non-volatile memory and is compared to a hardwiredvalue to determine if the metadata is valid. If the Signature (and hencethe metadata) is valid, the controller module loads the metadata intoits internal control and status registers to restore the configurationfor future SAVE and RESTORE operations. If the Signature is not valid,the controller module initializes the SSD/Flash memory and writesmetadata to it. For example, writing a value different from thehardwired value to the NV Signature register causes the next signaturecomparison to fail and render stored metadata invalid.

The information stored at the metadata area also facilitates selectivestorage of volatile memory content. The “Start Address” and “EndAddress” data are pointers defining the location where the content ofvolatile memory is stored. Depending on the implementation, the data reaof the non-volatile memory may store only a portion of the volatilememory content or multiple instance of the volatile memory content(e.g., providing capability to restoring to earlier states), and the“Start Address” and “End Address” allocate the storage space for thesedata.

Since multiple instances of the volatile memory content may be stored,more than one sets of pointers may be needed. For example, the “LBA0”set of pointers are directed to the location of a first instance ofvolatile memory content, while the “LBA1” set of pointers are directedto the location of a second instance of volatile memory content, and soon and so forth.

Often, for debugging and logging purposes, it may be advantageous tostore information related to the operation conditions of the iSC system.For example, the “Scatchpad0” and “Scatchpad1” data store informationthat may be used for firmware version control, debugging, and/or otherpurposes. Similarly, the “NV Debug” registers store debugginginformation, which can be used to change operation and behavior of theiSC system.

The controller module interfaces the volatile memory and controls itsoperations. To do so effectively, the controller module may rely on thespecific characteristics, parameters (e.g., read and write speed,frequency, latency, etc.) and organization of the volatile memory. Forexample, even for the same models, each SDRAM memory chip may havedifferent command, clock, and data delays to/from the controller module.In various embodiments, the controller module obtains performanceinformation that is specific to the memory chip that it interfaces, andadjust its operations accordingly. For example, various parameters andcharacteristics are stored at “SDRAM control”. Accordingly, trainingdata registers “Context Training” store parameters of memory module atdifferent contexts (e.g., different voltage level, frequency, etc.).

In various embodiments, contents are stored and/or updated at themetadata area of the non-volatile memory at the beginning of a SAVE orRESTORE execution as a baseline. It is then updated after the completionof the execution. This way the baseline status is retained even if apower failure occurs while an execution is in progress and the executionnever completes. The baseline status for a SAVE or RESTORE operation isset to “Fail to Complete”. It is updated to ‘Complete Successfully” onlyafter the operation is complete. This way there is no false positive ifthe operation was interrupted and never completed for any reason. It isto be appreciated that this operation prevents a false positiveoperation that can result in corrupted volatile memory image beingrestored and causing system crash.

FIG. 3 is a simplified flow diagram illustrating a processing for savingvolatile memory content according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. For example,various steps shown in FIG. 3 may be added, replaced, removed, modified,rearranged, and/or overlapped, which should not limit the scope ofclaims.

At step 301, a data area and a metadata area are defined on anon-volatile memory. For example, data area and the metadata area areillustrated in FIG. 2. It is to be appreciated that the non-volatilememory may have other area or region for storing other types of data. Incertain embodiments, the data area is capable of storing more than oneimage data of the volatile memory.

At step 302, a failure event is detected. For example, the failure eventcan be power failure, system failure, power off operation, or otherevents. As explained above, the iSC system includes a backup powermodule that powers the system for backup operations through the failureevent. In a specific embodiment, the controller module senses a voltagedrop, which is an indication of potential power failure, and thecontroller module initiates the backup process.

At step 303, at least a portion of the data area for storing a contentof a volatile memory is allocated. The controller module determineswhich area of the data area is to be used for storing content of thevolatile memory.

At step 304, the location of the portion of the data area is stored atthe metadata area. For example, the control module stores the locationof backup data using predefined pointer registers at the metadata area.

At step 305, operating parameters of the memory system are stored at themetadata area. The operating parameters comprises information related tocharacteristics of the volatile memory. For example, operatingparameters are stored at predefined locations of the metadata areaaccording to Table 1 above. The characteristics of the volatile memorymay include information such as latencies, frequencies, organization,and others. For example, the operating parameters may be empiricallydetermined by the controller module through operating the volatilememory.

At step 306, the content of the volatile memory is stored at the portionof the data area. For example, the content of the volatile memory may bestored in its entirety as an image of the volatile memory. In certainembodiments, only a portion of the volatile memory is stored.

At step 307, one or more signature data is stored at the metadata area.For example, the one or more signature data include one or moresignature registers, such as “Signature Low” and “Signature High”registers listed in Table 1. For example, since the signature data isstore after other storing process are performed, validity of thesignature data implies validity of other contents stored earlier.

FIG. 4 is a simplified flow diagram illustrating a processing forrestoring volatile memory content according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. Forexample, various steps shown in FIG. 4 may be added, replaced, removed,modified, rearranged, and/or overlapped, which should not limit thescope of claims.

At step 401, the controller module interfaces the nonvolatile memory andobtains a signature data stored at a metadata area of a non-volatilememory. As described above, the non-volatile memory comprises themetadata area and a data area. The controller module uses the signaturedata to determine the validity of information stored both at themetadata area and the data area of the non-volatile memory.

At step 402, the validity of the previous data backup is determined.More specifically, the signature data is compared to a reference data.For example, the reference data is hardwired. If the signature data isthe same as the reference data, the previous backup is valid. On theother hand, if the signature data is different from the reference data,the previous backup is invalid.

If the backup event is valid, a restore process is performed. At step403, operating parameters are obtained from the metadata area of thenon-volatile memory. The operating parameters include register andstatus information for operating the controller module and/or volatilememory parameters. The operating parameters allow the controller moduleand the non-volatile memory to operate in optimal condition.

At step 404, a controller module operates in accordance with theoperating parameters. For example, during a restoring operation, thecontroller module resumes the operation of its FSMs by using the loadingthe register values and status information stored at the metadata areaof the non-volatile memory. For example, the controller module rely onthese operating parameters (e.g., speed, size, location, etc.) forcopying backup data stored at the data area of the non-volatile memoryto the volatile memory.

At step 405, a first content stored at the data area is copied to thevolatile memory. In a specific embodiment, the nonvolatile memory storesmore than one backup images of the volatile memory, and the controllermodule selects one of the backup images to be used. For example, thedefault operation may be to copy the latest backup image, but it may bedesirable to use an earlier version if the latest backup image iscorrupted or otherwise unusable.

Now referring back to step 402. If the backup event is invalid, thebackup content stored at the nonvolatile memory is not to be used. Atstep 406, the metadata area is initialized using at least a predetermineset of parameters. Since operations are performed by the controllermodule, the controller module is initialized and operates from a defaultstarting state. Accordingly, corresponding parameters are stored at themetadata area of the nonvolatile memory.

At step 407, the memory system is initialized. For example, a set ofdefault parameters is used to operate the controller module and othercomponent of the iSC system. For example, the set of default parametersinclude parameters for operating the controller module, volatile memory,non-volatile memory, interfacing the host controller, and/or otheroperations.

It is to be appreciated that the controller module for the memory systemcan be implemented in various ways. FIG. 5 is a simplified diagramillustrating a controller module 500 according to an embodiment of thepresent invention. This diagram is merely an example, which should notunduly limit the scope of the claims. One of ordinary skill in the artwould recognize many variations, alternatives, and modifications. As anexample, the memory controller module 500 uses a data path illustratedin FIG. 2 and can execute the processes illustrated in FIGS. 3 and 4.

The controller module 500 includes a buffer 501, which provides a datapath and electrical buffer. As shown in FIG. 5, the buffer 501 comprisesa load reduction memory buffer. For example, the buffer 501 isintegrated as a part of the controller module chip. The buffer 501 isconnected to the host interface 530 and the volatile memory (e.g., DRAM)interface 520. Through the buffer 501, data from a host system can betransmitted to the volatile memory. Additionally, the buffer 501provides electrical buffer to reducing the loading power of on the I/O,thereby improving system efficiency and reliability.

The controller module 500 further includes a memory controller 502. Itis to be appreciated the memory controller 502 is configured to operatewhen the host is not operating. For example, in normal operation mode,the host provides control functions for moving information back andforth between the host and the volatile memory; in failure mode (e.g.,power down), the host is incapable of providing control functions, andthe memory controller 502 takes over and provides control function formoving information (e.g., backing up information stored at the volatilememory to the non-volatile memory). In various implementations, thememory controller 502 is configured to operate at a high speed toquickly move data from the volatile memory to the non-volatile memoryfor backup. For example, in failure mode, the volatile memory haslimited residual power (or back up power provide by a backup powermodule) for self-refresh and keep data alive, and the residual power ofthe volatile memory dictates the time window, during which the memorycontroller can back information stored at the volatile memory. Forexample, in failure mode, the memory controller 502 causes the datastored at the volatile memory to be transferred from the interface 520to the non-volatile memory. In certain embodiments, the memorycontroller 502 can also reprogram the volatile memory. Additionally, thememory controller 502 may operate during normal operating mode forbacking up data to the non-volatile storage.

The controller 503 provides save and restore functions. Morespecifically, the controller 503 is configured to receive indication oftriggering event (e.g., power failure, power on, etc.). Among otherfeatures, the controller 503 facilitates and coordinates save andrestore processes with other controllers of the controller module 500.

The controller 503 is connected to the driver 504. For example, thedriver 504 comprises an advanced host controller interface (AHCI)driver, which provides interfacing with the host. For example, thedriver 504 provide driving functions for the host controller. Accordingto various implementations, the driver 504 receives commands from theFSMs (e.g., FSM 508 and FSM 509) to executable instructions for variouscontrollers of the of the controller module 500. For example, thecommands include command execution and sequence execution. It is to beappreciated the driver 504 may include other modules addition to orinstead of the AHCI driver.

The driver 504 is connected to the controller 505. The controller 505comprises a non-volatile memory (e.g., SSD/flash) interface. Thecontroller 505 provides controller and I/O functions with thenon-volatile memory. For example, during a SAVE event, the content ofthe volatile memory is copied to the non-volatile memory via thecontroller 505; during a RESTORE event, the content of the non-volatilememory is copied to the non-volatile memory, also via the controller505.

The drive 504 is connected to the memory controller 502 via Tx buffer506 and the Rx buffer 507. According to various embodiments, the Txbuffer 506 and the Rx buffer 507 are data buffers implemented using highspeed volatile memory devices (e.g., SRAM). It is to be appreciated thatthe data buffers Tx buffer 506 and the Rx buffer 507 provide speedmatching between the non-volatile memory and the volatile memory. Forexample, volatile memory typically operates much faster (e.g., 20 timesor higher) than non-volatile memory. To transfer data betweennon-volatile memory and volatile memory, data are first buffer at the Txbuffer 506 and the Rx buffer 507 so that the non-volatile memory cantransfer a block (instead of a stream) of data at a time. For example,the Tx buffer 506 and the Rx buffer 507 allow for data throttling andburst mode operation. The Tx buffer 506 and the Rx buffer 507 can beused to keep the non-volatile memory operating at a stable speed, whileconserving power consumption for the volatile memory.

The controller module 500 additionally includes an SMBus 511. Forexample, the SMBus 511 is implemented as a serial bus operating in slavemode. Among other features, the SMBus 511 provide an interface foraccessing the controller module 500, and can be used for program andupdating various functions of the controller module 500.

The register block 510 comprises a number of registers, and is used byvarious controllers (e.g., controllers 503, 502, 505, etc.) and/or othercomponents. For example, the registers are used to store variousparameters and settings need for operating various controllers andcomponents of the controller module 500. As an example, the registerblock 510 provides the function for the register module 224 is FIG. 2.

It is to be appreciated that the controller module 500 can beimplemented in various ways, and FIG. 5 merely provides an simplifiedfunctional block diagram. Various components may be added, removed,replaced, or modified.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A memory system comprising: a non-volatilememory, the non-volatile memory comprising a data area and a metadataarea, the metadata area being predefined to store system parameters; avolatile memory comprising a plurality of SDRAM memory modules; a backuppower module; and a controller module having a host interface and aplurality of registers, the controller module being configured totransfer data received from the host interface to the plurality of SDRAMmemory modules via various types of bus lines; wherein: in a SAVE event,the controller module is configured to cause the non-volatile memory tostore at least content of the plurality of registers and signature dataat the metadata area and store content of the volatile memory at thedata area, wherein the content of the plurality of registers comprisestraining data of an organization parameter of the plurality of SDRAMmemory modules at different contexts; in a RESTORE event, the controllermodule is configured to determine a validity of the content stored atthe data area using at least the signature data, and the controllermodule causes the content stored at the data area to be copied to thevolatile memory if the content at the data area is determined to bevalid; and the controller module comprises a reference signature valuefor comparing to the signature data.
 2. The system of claim 1 whereinthe backup power module comprises a super capacitor.
 3. The system ofclaim 1 wherein the controller module further comprising a sequenceexecution FSM and a command execution FSM.
 4. The system of claim 1wherein the non-volatile comprises a flash memory and/or a solid statedrive.
 5. The system of claim 1 wherein the control modules causes thenon-volatile memory to store parameters related to the volatile memory.6. The system of claim 1 wherein the SAVE event is triggered by a systempower failure.
 7. The system of claim 1 wherein the controller module isconfigured to generate performance characterization data for thevolatile memory and to store the performance characterization data atthe metadata area.
 8. The system of claim 1 wherein in the RESTOREevent, the controller module retrieves operating parameters from themetadata area.
 9. The system of claim 1 wherein the data area isconfigured to store multiple instances of the volatile memory.
 10. Amethod for preserving volatile memory data for a memory system, themethod comprising: defining a data area and a metadata area on anon-volatile memory; detecting a failure event; allocating at least aportion of the data area for storing a content of a volatile memorycomprising a plurality of SDRAM memory modules connected via varioustypes of bus lines; storing a location of the portion of the data areaat the metadata area; storing organization parameters of the memorysystem at the metadata area, the organization parameters comprisinginformation related to characteristics of the volatile memory; storingat the metadata area, training data of the organization parameters atdifferent contexts; storing the content of the volatile memory at theportion of the data area; and updating one or more signature data storedat the metadata area for use in determining validity of the contentduring a future restore event by comparison with a reference signaturevalue of a controller.
 11. The method of claim 10 further comprisingstoring debugging information at a predefined region of the metadataarea.
 12. The method of claim 10 further comprising: determiningoperating characteristics of the volatile memory; storing the operatingcharacteristics of the volatile memory to a predefined location on themetadata area.
 13. The method of claim 10 further comprising determininga location on the data area for storing the content of the volatilememory.
 14. The method of claim 10 further comprising selective storinga portion of the content of the volatile memory.
 15. A method forrestoring operation and data for a memory system, the method comprising:obtaining a signature data stored at a metadata area of a non-volatilememory, the non-volatile memory comprising the metadata area and a dataarea; comparing the signature data to a reference signature data of acontroller module to determine whether a previous backup event is valid;if the previous backup event is valid: obtaining SDRAM organizationparameters from the metadata area; obtaining from the metadata area,training data of the organization parameters of a controller moduleconnected via a variety of different bus lines to a plurality of SDRAMmemory modules, at different contexts; operating the controller modulein accordance with the organization parameters; copying a first contentstored at the data area to a volatile memory comprising the plurality ofSDRAM memory modules; if the previous backup event is invalid:initializing the metadata area using at least a predetermine set ofparameters; initializing the memory system.
 16. The method of claim 15further comprising selecting between the first content and a secondcontent at the data area, the first content and the second content beingdifferent image data of volatile memory.
 17. The method of claim 15wherein the metadata area further comprises operating parameters thatinclude information related to performance characteristics of thevolatile memory.
 18. The method of claim 17 wherein the operatingparameters include register values for operating one or more FSMs of thecontroller module.